Superoxide mediated isomerization of 4-aryl-but-1-ynes to 1-aryl-1,3-butadienes

Khan, Faiz Ahmed and Budanur, B M (2015) Superoxide mediated isomerization of 4-aryl-but-1-ynes to 1-aryl-1,3-butadienes. Tetrahedron, 71. pp. 7600-7607. ISSN 0040-4020

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Abstract

A new role of superoxide ion in the isomerization of homobenzylic acetylenes leading to 1-aryl-1,3-butadienes is reported. The unconventional reagent KO2 is found to be superior in performing this kind of isomerization over other the commonly used bases. For substrates containing arene moiety and triple bond connected through more than two methylene groups, and for propargylcyclohexanol the reagent selectively effected migration of the triple bond. Reactivity of KO2 towards the substrates having disubstitution at benzylic position varied depending on the nature of the substitution, alkyl-substitution lead to isomerization to give mixture of allene (an intermediate in the isomerization of acetylene to 1,3-butadiene) and triple bond migration product; whereas phenyl-substituted compound gave 1,3-diene. The utility of the methodology was demonstrated through a Diels–Alder reaction of one of the dienes obtained by the isomerization with suitable dienophiles.

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